1. Field
Example embodiments relate to a method of forming an electrode of a variable resistance memory device and a variable resistance semiconductor memory device using the electrode.
2. Description of the Related Art
Semiconductor memory devices may be classified into volatile memory devices and nonvolatile memory devices. The nonvolatile memory devices retain their stored data even when power to the nonvolatile memory devices is cut off. Examples of nonvolatile memory devices may include a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically EPROM (EEPROM), and a Flash Memory Device. A demand for nonvolatile memory devices that are capable of repeatedly performing read and write operations has been increased.
With regard to nonvolatile memory devices, variable resistance memory devices, for example, a Resistive Random Access Memory (ReRAM) and a Phase-change Random Access Memory (PRAM), are being developed currently. Materials constituting these variable resistance memory devices have variable resistance values according to current or voltage and maintain their resistance values even when current or voltage supply is cut off.
PRAM uses a phase change material, for example, a chalcogenide. The phase change material has a crystalline state and an amorphous state according to temperature variation. When a phase change material layer of an amorphous state is heated for a predetermined time at a temperature between a crystallization temperature and a melting point temperature and then is cooled, it changes from the amorphous state into a crystalline state (set programming). On the contrary, when the phase change material layer is heated at a higher temperature than the melting point temperature and then cooled drastically, it changes from a crystalline state into an amorphous state (reset programming).